332
T H E J O U R N A L OF INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
Vol. 13, NO. 4
Notes on Laboratory and Demonstration Apparatus1 By Clifford D. Carpenter DEPARTMENT OF CHEMISTRY, COLUMBIA UNIVERSITY, NEW YORK,N. Y. APPARATUS FOR DEMONSTRATING THE VAPOR PRESSURE O F LIQUIDS
The apparatus herein illustrated shows five Torricelli tubes standing in a special overflow trough. The principal feature is t h a t the inner trough is small and uses little mercury, and the sides are low so t h a t the mercury runs over into the outer trough when too full. This gives a constant zero point a t the lower end of the tubes. The cross-section, g, gives t h e detail. Two rods, each 3 f t . in length, are screwed into the ends of the inner trough and are used as supports for a crossbar by which the tubes are held in position. I n practice a rubber band or cordis sufficient t o hold the tubes in place against t h e crossbar, Tube d is fitted into a large stopper which closes the lower end of a large tube used as a jacket. This large open tube has 9 a n outlet, f , a t its lower end, making it p o s s i b l e t o change t h e water and t o surround d with water a t definite temperatures. Tubes d and e are graduated in mm. from the bottom upward, making i t possible t o read the height of the mercury column directly. I n a demonstration all tubes are filled with mercury and inverted, and the heights of the columns noted. The jacket about d is filled with water a t room temperature. By the aid of pipets, h , water is introduced into d , alcohol into c, chloroform into b , and ether into a, while e is left as a comparison tube. Attention may then be called t o t h e relative vapor pressures of the different substances. If tubes d or e are not graduated a meter stick may be used. The depression of the mercury in d i s measured and the temperature noted. Water of a different temperature is then introduced into the jacket around d and the depression and temperature again noted, and the results are compared with the aqueous tension tables given in the handbooks.
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A BINGSTALND BET
Mobility of apparatus after i t is assembled for use in a n experiment is most desirable. This is especially 1
Received December 7, 1020.
true in the case of a lecture demonstration, for if each experiment can be set out in some prominent place while under discussion, the pupils can follow the procedure much more readily t h a n when the experiment is one of a long line arranged from one end of t h e desk
FIG.1
t o the other. A slight alteration in t h e common ringstand makes it possible t o mount the apparatus used in many experiments, ordinarily requiring two or more supports, upon a single support. The illustrations in Figs. 1 and 2 show two simple alterations which have been found very practical a n d useful. Such modifications would also prove very useful t o students. Each student could be provided with a ringstand set as follows: a base 7 in. X 10 in. and three interchangeable rods; a straight rod 26 in.X 0.375 in. which, when mounted in the base, would give the ordinary ringstand; a second rod 36 in. X 0.375 in. bent a t right angles, so t h a t when mounted in the base t h e horizontal portion is 11 in. above the base, as illustrated in Fig. 1; and a third rod 36 in. X 0.375 in. bent so t h a t the two portions make a n angle of 75”, as illustrated in Fig. 2, so t h a t when mounted the perpendicular portion is about 18 in. in length.
FIO.2
While t h e rods may be screwed into the base i t is not entirely satisfactory, a s rusting and wear will gradually make t h e interchange of rods difficult. Moreover, t h e bent rods must always take the same position with respect t o the base when mounted. This difficulty is easily overcome by using a “lock socket.’’
Apr., 1921
THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
333
LABORATORY SINK
The accompanying sketch illustrates a convenient f o r m of sink for laboratories in elementary and general chemistry. The main feature of t h e sink is its three compartments. The two smaller compartments drain into the larger center compartment by a 1-in. hole, c, which can be closed by a stopper. When filled with water i t overflows into the center compartment. These smaller compartments are intended t o be used €or collecting gases. When in use i t is not necessary t o stop up the whole sink and make i t entirely useless t o all other students. T h e sink is designed t o be used by four students, two on either side of t h e desk. Three water faucets, a, a, K , are illustrated. a and a are small a n d , t a p e r ing, making them especially adapted for attaching rubber tubing for condensers, etc. The sink is made of albarine stone and as illustrated is 32 in. X 16 in. outside dimensions. The smaller compartments are 14 in. X 5 in. X 4 in. deep on the lower overflow side, which is 0.5 in. lower t h a n the top of the sink. The larger compartment is 18 in. X 14 in. X 10 in. deep. The drain is in the middle of
the large compartment and is protected by a sieve. The size of the sink can be altered t o suit any space.
Solvents for Phosgene' By Charles Baskerville and P. W. Cohen COLLEGE OF TH$ CITYOF NEWYORK, NEW YORK,N. Y.
After the signing of the armistice, restrictions were placed on railroad transportation of liquefied phosgene in the United States. Previous t o 1914 small cylinders of the liquid were imported from Germany t o be used in producing a limited number of carbon compounds and for research purposes. It was produced in the country on a small scale after the blockade and before we entered the war, and was distributed in cylinders. Immense quantities were on hand when hostilities ceased. The greatest danger in t h e transportation of phosgene, liquid or in solution, would arise in case of fire or wrecks. Protection against leaky valves is quite simple. While the demand for phosgene for t h e purposes mentioned is not great from the quantity point of view, nevertheless i t exists. Oft expressed have been the hopes of finding more extensive uses for the poison gases of the World War in peace times. It seemed, therefore, worth while t o endeavor t o find other means for t h e transportation of and other applications for phosgene. Among other qualifications, a liquid solvent for phosgene should be (1) inert t o carbonyl chloride, (2) have a low vapor pressure, (3) hold notable amounts in solution, (4) admit of easy recovery of the gas, (5) preferably be noninflammable, and (6) involve minimum expense. T h e first and last of these qualifications are t h e most important, the former being primarily due t o the reactivity of phosgene. As a general statement i t may be said t h a t phosgene is soluble in ether, chloroform, liquid hydrocarbons, 1 Presented before the Division of Industrial and Engineering Chem. istry a t the 60th Meeting of the American Chemical Society, Chicago, Ill., September 6 to 10. 1920.
carbon disulfide, and sulfur chloride, as well as in some of the liquid metal chlorides (stannic chloride and antimonic chloride). The following liquids were used by us as solvents: carbon tetrachloride, chloroform, gasoline, paraffin oil, Russian mineral oil, benzene, toluene, glacial acetic acid, ethyl acetate, a n d chlorocosane. The last substance is paraffin which has been melted and treated with chlorine. It forms a light yellow compound, t h e formula of which has not yet been determined. This compound is used medicinally t o dissolve dichlora mine-T . The method of procedure was t o pass the gas through a Bowen's absorption bulb containing t h e solvent a t atmospheric pressure. The solution was stoppered well in a dry test tube and allowed t o stand for 2 wks. Various tests were made on each solution t o detect any evidence of reaction. The following is a table of results for the solvents mentioned above: Evidence of Weight Solubility Weight Phosgene Ratio by Reaction Solvent Absorbed Weight on SOLVENT Grams Grams COClzSolvent Solution Carbon tetrachloride 79.5 22 1 : 3.6 None Chloroform.. 49.4 29 1 : 1.7 Gasoline. . 37.0 30 1 : 1.2 34.6 0 0 Paraffin oil.. Russian mineral oil. 30. 1 10.8 1 : 2.8 Benzene.. , 43.9 43.6 1 : 1 None Toluene., , . . 50.3 33.5 1 : 1.5 Glacial acetic acid. 31 .4 19.5 1 : 1.6 Ethyl acetate.. 20.5 20.2 1: 1 None Chlorocosane.. 25.2 7.8 1 : 3.2 None
.... .. . . . .. .. .. .. .. .. .. . ..... .. .. .. .. .. . .... .... ..
Comments by Numbers Below 1 2 3
4 5 6
7 8 9 10
All weighings were made a t 20" to 21' C. The ratio values are not given with mathematical accuracy for obvious reasons. (1) With carbon tetrachloride no evidence of reaction was observed. The boiling point of the solvent was the same before and after saturation with phosgene.
